there are times when you employer cannot give you a w2 for various reasons, this page gives you information about how obtain a W2 form and get it yourself 
I was in a situation where my employer (boss) was no longer in business. i tried to get a w2 form from them but they went out of business, i was lost, i didnt know what to do.
well if you are in the same situation as i was, you can use IRS Form 4852 to create a w2 yourself.
its very easy to fill out, you only have to fill out 10 questions and sign it.
you can download it at:
hope this helps. i want to help other people with their tax problems, tell me what why do you think you didnt get a W2 form?